1. Field of the Invention
The present invention relates generally to lithium batteries.
2. Description of the Related Art
Secondary batteries are batteries which are designed to be recharged and used multiple times, unlike primary batteries. Recently, a lot of research into such secondary batteries is being conducted along with development of high technology fields related to, for example, digital cameras, cellular phones, notebook computers, hybrid vehicles, etc. Nickel-cadmium batteries, nickel-metal hydride batteries, lithium secondary batteries, etc. are representative examples of the secondary batteries. Among such examples, the operating voltage of the lithium secondary batteries (hereinafter, referred to as ‘lithium batteries’) ranges from 2.0 V to 4.2 V or may be higher. Such a lithium battery may be typically used as a power supply for mobile electronic devices, or a plurality of lithium batteries may be connected in series to each other and used in a high power hybrid vehicle. The operating voltage of the lithium batteries is three times greater than that of nickel-cadmium batteries or nickel-metal hydride batteries. The energy density per unit weight of the lithium batteries is also comparatively high. Therefore, the use of the lithium batteries is rapidly increasing.
Such a lithium battery includes a bare cell which includes battery tabs through which power is input or output, and a case in which the bare cell is housed. Here, the bare cell that is housed in the case is called a battery cell.
The battery cell includes a pouch type bare cell and a battery cell case. The battery cell case includes a front case plate and a rear case plate which are disposed on front and rear surfaces of the bare cell and are separably coupled to each other to protect the bare cell.
In conventional battery cell cases, a front case plate and a rear case plate are made of metal or adiabatic plastic and are coupled to each other while in close contact with the front and rear surface of a bare cell. The front and rear case plates are fastened to each other by screws or bolts after having been put in close contact with each other.
As such in the case of the conventional battery cell cases, the process of fastening the front case plate to the rear case plate includes inserting bolts or screws into the front and rear case plates and tightening the bolts or screws using a tool, such as a screwdriver or wrench. Therefore, the working time required to assemble the battery cell case is increased, thus reducing productivity.
Furthermore, in the case of a lithium battery using the conventional battery cell, typically, a plurality of battery cells are contained in a single case and are connected in series or parallel to each other, thus forming a medium-large sized lithium battery that can be used as a high-voltage power supply in an industrial site.
The medium-large sized lithium battery generally includes ten or more battery cells that are electrically connected to each other. Such medium-large sized lithium batteries have been used in places where industrial or large-capacity power is needed. On the other hand, in the case of a lithium battery for domestic or portable use, two to ten battery cells are typically connected in series or parallel to each other.
As such, the conventional lithium batteries can be electrically connected to each other to produce a required amount of power. However, the connection between the lithium batteries is just an electrical connection in which the lithium batteries are mechanically separated from each other. Therefore, accidents caused by negligence may occur at industrial sites, and it may become an inconvenience for pedestrians.
Moreover, in the conventional lithium battery having one or more bare cells, a comparative large volume case that houses each bare cell increases the size of the entire lithium battery. The greater the capacity of the lithium battery is, the larger is the size of the entire lithium battery. Therefore, it is very inconvenient to transfer or store the lithium battery.